From c217453c85aaba7a8cde7cb3ddbd8eba59d1fba9 Mon Sep 17 00:00:00 2001
From: Pekka Paalanen <pekka.paalanen@collabora.com>
Date: Thu, 22 Jul 2021 16:33:51 +0300
Subject: [PATCH] backend-drm: forward HDR metadata

Forward the HDR Static Metadata Type 1 to the video sink. This makes the
sink aware of our video content parameters and may be able to produce a
better picture. This type of metadata is used only with the ST 2084 HDR
mode a.k.a PQ.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>
---
 libweston/backend-drm/kms-color.c | 78 ++++++++++++++++++++++++++++++-
 libweston/backend-drm/meson.build |  1 +
 2 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/libweston/backend-drm/kms-color.c b/libweston/backend-drm/kms-color.c
index ae479754..8219c94c 100644
--- a/libweston/backend-drm/kms-color.c
+++ b/libweston/backend-drm/kms-color.c
@@ -29,13 +29,86 @@
 #include <libweston/libweston.h>
 #include <assert.h>
 #include <string.h>
+#include <math.h>
 
 #include "drm-internal.h"
 #include "libdrm-updates.h"
 
+static inline uint16_t
+color_xy_to_u16(float v)
+{
+	assert(v >= 0.0f);
+	assert(v <= 1.0f);
+	/*
+	 * CTA-861-G
+	 * 6.9.1 Static Metadata Type 1
+	 * chromaticity coordinate encoding
+	 */
+	return (uint16_t)round(v * 50000.0);
+}
+
+static inline uint16_t
+nits_to_u16(float nits)
+{
+	assert(nits >= 1.0f);
+	assert(nits <= 65535.0f);
+	/*
+	 * CTA-861-G
+	 * 6.9.1 Static Metadata Type 1
+	 * max display mastering luminance, max content light level,
+	 * max frame-average light level
+	 */
+	return (uint16_t)round(nits);
+}
+
+static inline uint16_t
+nits_to_u16_dark(float nits)
+{
+	assert(nits >= 0.0001f);
+	assert(nits <= 6.5535f);
+	/*
+	 * CTA-861-G
+	 * 6.9.1 Static Metadata Type 1
+	 * min display mastering luminance
+	 */
+	return (uint16_t)round(nits * 10000.0);
+}
+
+static void
+weston_hdr_metadata_type1_to_kms(struct hdr_metadata_infoframe *dst,
+				 const struct weston_hdr_metadata_type1 *src)
+{
+	if (src->group_mask & WESTON_HDR_METADATA_TYPE1_GROUP_PRIMARIES) {
+		unsigned i;
+
+		for (i = 0; i < 3; i++) {
+			dst->display_primaries[i].x = color_xy_to_u16(src->primary[i].x);
+			dst->display_primaries[i].y = color_xy_to_u16(src->primary[i].y);
+		}
+	}
+
+	if (src->group_mask & WESTON_HDR_METADATA_TYPE1_GROUP_WHITE) {
+		dst->white_point.x = color_xy_to_u16(src->white.x);
+		dst->white_point.y = color_xy_to_u16(src->white.y);
+	}
+
+	if (src->group_mask & WESTON_HDR_METADATA_TYPE1_GROUP_MAXDML)
+		dst->max_display_mastering_luminance = nits_to_u16(src->maxDML);
+
+	if (src->group_mask & WESTON_HDR_METADATA_TYPE1_GROUP_MINDML)
+		dst->min_display_mastering_luminance = nits_to_u16_dark(src->minDML);
+
+	if (src->group_mask & WESTON_HDR_METADATA_TYPE1_GROUP_MAXCLL)
+		dst->max_cll = nits_to_u16(src->maxCLL);
+
+	if (src->group_mask & WESTON_HDR_METADATA_TYPE1_GROUP_MAXFALL)
+		dst->max_fall = nits_to_u16(src->maxFALL);
+}
+
 int
 drm_output_ensure_hdr_output_metadata_blob(struct drm_output *output)
 {
+	const struct weston_hdr_metadata_type1 *src;
 	struct hdr_output_metadata meta;
 	uint32_t blob_id = 0;
 	int ret;
@@ -43,6 +116,8 @@ drm_output_ensure_hdr_output_metadata_blob(struct drm_output *output)
 	if (output->hdr_output_metadata_blob_id)
 		return 0;
 
+	src = weston_output_get_hdr_metadata_type1(&output->base);
+
 	/*
 	 * Set up the data for Dynamic Range and Mastering InfoFrame,
 	 * CTA-861-G, a.k.a the static HDR metadata.
@@ -72,6 +147,7 @@ drm_output_ensure_hdr_output_metadata_blob(struct drm_output *output)
 		break;
 	case WESTON_EOTF_MODE_ST2084:
 		meta.hdmi_metadata_type1.eotf = 2; /* from CTA-861-G */
+		weston_hdr_metadata_type1_to_kms(&meta.hdmi_metadata_type1, src);
 		break;
 	case WESTON_EOTF_MODE_HLG:
 		meta.hdmi_metadata_type1.eotf = 3; /* from CTA-861-G */
@@ -83,8 +159,6 @@ drm_output_ensure_hdr_output_metadata_blob(struct drm_output *output)
 		return -1;
 	}
 
-	/* The other fields are intentionally left as zeroes. */
-
 	ret = drmModeCreatePropertyBlob(output->backend->drm.fd,
 					&meta, sizeof meta, &blob_id);
 	if (ret != 0) {
diff --git a/libweston/backend-drm/meson.build b/libweston/backend-drm/meson.build
index e913f4b9..cb2ebda0 100644
--- a/libweston/backend-drm/meson.build
+++ b/libweston/backend-drm/meson.build
@@ -38,6 +38,7 @@ srcs_drm = [
 ]
 
 deps_drm = [
+	dep_libm,
 	dep_libdl,
 	dep_libweston_private,
 	dep_session_helper,